An earbud is an earphone that is to be partially inserted into the outer ear canal. When seeking to improve the acoustic bass response of a loose fitting, earbud-type speaker driver, an acoustic bass tuning tube (that is open to the atmosphere) can be added that connects to a back volume chamber of the driver. The back volume chamber is separated from a front volume chamber by the diaphragm of the driver, and contains a volume of air inside the earbud housing that is open to the rear face of the driver diaphragm. The tuning tube provides the needed, equivalent acoustic mass loading to the driver, so as to lower the frequency of the driver's resonance, to thereby yield an extended low frequency or bass response. This is effective for improving bass response when there is acoustic leakage that is due to the loose fit of the earbud.